The present invention relates to a system for the modification of a prosthesis so that the basic prosthesis can be used in normal surgical procedures and in which certain surfaces can also be adjusted to be used in revision knee surgery or in normal surgery when it is desired to augment the thickness of the prosthesis at various bone contact surfaces. For example, in the case of revision surgery, a previously implanted knee prosthesis may have failed for a number of different reasons. These reasons include a malpositioning of the prosthesis on original implantation, loosening of the prosthesis, infection, or dislocation. These categories are not necessarily exclusive because infection, for example, may cause a loosening of the prosthesis which in turn, may cause dislocation. In some instances, it is necessary to remove additional bone during revision surgery because of bone infection, or because of stems fractures or fatigue fractures of the prosthesis and resulting bone damage.
In addition to its use in revision prosthesis, the present prosthesis may also be used in the initial implantation surgery. On occasion, a surgical procedure cannot be carried out as planned because during the surgical procedure it is discovered that a particular area of bone is not adequate to support the prosthesis intended to be implanted. In the case of revision surgery or in situations where X-ray or other imaging indicates a problem with the bone, it is possible to custom make a prosthesis to fit a particular patient and overcome the problems of implantation. However, it would be preferable to have the capability of modifying a prosthesis during the surgical procedure in the event that untoward problems become evident during the surgical procedure.
Previously used procedures for modifying the bone contact surface of tibial components of a knee prosthesis include drilling holes in the prosthesis and attaching the augmentation component with bolts or screws or cementing the augmentation devices to the distal or bone contact side of the prosthesis.
U.S. Pat. No. 4,995,883 discloses a hip prosthesis with adjustment pads which may be used to increase the thickness of the prosthesis in selected areas. The pads are secured in position on the body of the prosthesis using bolts and/or expandable bushings.